Block copolymers have been formulated to produce a number of types of adhesive compositions. The basic patent in this field, Harlan, U.S. Pat. No. 3,239,478, shows combinations of block copolymers with tackifying resins and oils to produce a wide spectrum of adhesives. While these are suitable for many purposes, the prior art compositions are usually deficient in one physical property or another leaving something to be desired for specific applications. In many cases, the deficiency lies in the area of high temperature properties. For example, Russell, U.S. Pat. No. 635,861 shows hot melt adhesives comprising block polymer, certain resins and oil. However, the high temperature properties of the described adhesive compositions are deficient.
It would be desirable to be able to apply an adhesive to a backing in the form of a melt, but if viscosity-reducing components are absent, the melt is then of such high viscosity that the equipment normally available for this purpose cannot handle the composition. An example of this is shown in Korpman, U.S. Pat. No. 3,676,202, which describes a 2-component blend of certain block copolymers with a particular type of tackifying resin. However, the compositions described by Korpman are clearly oil-free and consequently would be difficult to apply to the tape in the form of a melt. They could be applied readily in the form of a solution as shown in Korpman's working examples. However, solvents add to the expense of the operation, increase fire hazards, and require expensive recovery equipment to avoid air pollution.